This invention relates to parts identification, and more particularly, to direct part marking with encoded symbology.
Industry utilizes part identification markings to relate parts and components to their respective histories. A wide range of marking methods has been developed for this purpose including means to apply to the part, machine-readable symbols or symbology of the type used for automatic data collection. Such symbology may include alpha-numeric characters, bar codes, stacked bar codes and/or 2D codes.
Available marking methods involve the use of attaching to a part, identification means; such as adhesive backed labels, tapes, bands, tags, identification plates or the like. Such marking methods may also include direct part markings (DPM), applied to, or formed by altering, a parts surface; such as shown and described in U. S. Pat. No. 1,561,427 issued on Nov. 19, 1925 to C. T. Forsberg for xe2x80x9cMethod And Means For Marking Castingsxe2x80x9d. Parts, as broadly referred to, may include an entire product, and/or the constituent assemblies, sub-assemblies and the individual component parts of the product.
DPM is generally recommended in applications where: 1) traceability is required after the part is separated from a temporary identification, such as marked packaging; 2) the part is too small to be marked with symbology coded labels or tags; or 3) the part is subjected to environmental conditions that preclude the use of an attached identification means that will not survive those conditions.
DPM may generally be subdivided into two general categories: non-intrusive and intrusive.
Intrusive marking methods alter a parts surface by abrasion, cutting, burning, vaporizing or other destructive means. Intrusive marking methods include methods such as micro-abrasive blast, dot peening, electrochemical etch, machine engraving, milling, laser etching and engraving or other similar marking methods.
Non-intrusive markings, also know as additive markings, can be produced as part of the manufacturing process: such as the mold and cast of said U.S. Pat. No. 1,561,427; forging; or by adding a layer of media to a parts surface using methods that have no adverse effects on material properties of the part. Molding of patterns into parts is also shown and described in U.S. Pat. No. 3,627,861 issued to R. F. Timke on Dec. 14, 1971 for xe2x80x9cMethod Of Forming Indented Decorative Patterns On Ceramic Tilesxe2x80x9d.
Examples of additive marking could be ink jet, silk screen, stencil or other similar marking methods; such as shown and described in U.S. Pat. No. 5,144,330 issued on Sep. 1, 1992 to C. G. Bennett for xe2x80x9cMethod And Apparatus For Printing On Pipexe2x80x9d and U.S. Pat. No. 5,831,641 issued on Nov. 3, 1998 to R. G. Carlson for xe2x80x9cMethods And Apparatus For Imprinting Indicia On A Three Dimensional Articlexe2x80x9d and in Defensive Publication T 909,002 published Apr. 3, 1973 for N. S. White, et al for xe2x80x9cIdentification Printer For Plastic Partsxe2x80x9d.
While both non-intrusive and intrusive marking methods are widely used in industry, their applications are limited. Non-intrusive markings are not generally used in applications associated with harsh environments. For instance, ink marking would not be used to mark engine components because the high heat experienced by the part would burn off the marking media. Intrusive markings, which were designed to survive harsh environments, are considered to be controlled defects in high stress applications and can degrade material properties beyond a point of acceptability.
Consequently, some intrusive markings, especially those done by lasers, are generally not used in safety critical applications without appropriate metallurgical testing and engineering approval. Safety critical applications include parts whose failure could result in hazardous conditions. Examples of safety critical applications are systems related to aircraft propulsion; vehicle control; equipment handling; high pressure; pyrotechnics and; nuclear, biological and chemical containment.
While it has been demonstrated that safe settings can be established through expensive and time consuming metallurgical testing, industry has never been conformable with this application because of the risk of input errors when entering settings. For example, an input error made during a turbine blade marking operation could result in the application of a marking that is applied with too much heat, resulting in micro-cracks that could propagate over time as the part is subjected to operational stresses. The aircraft industry has seen numerous situations where unknown defects in engine components have resulted in part failures leading to catastrophic engine loss. Many of these have involved flying debris that has been ingested by engines, penetrated cabins to strike passengers, punctured fuel tanks, cut control mechanisms and other damage. These incidents have often resulted in forced emergency landings or aircraft crashes involving fearful loss of life.
The aerospace industry especially requires methods to safely apply to parts, machine-readable encoded symbology that can withstand harsh environments. Many industry members currently utilize mold and cast techniques to create a part with raised or recessed characters representing part identification numbers (usually lot traceability). The impressions used to create the part identification characters are often stamped into molds using manual methods. While this process may have worked well for some industry members; it does not lend itself to automation.
With the recent release of Aircraft Transportation Association (ATA) Specification 2000, which requires the expanded use of machine-readable symbology markings, the aircraft industry has been looking for ways to automate the cast and mold marking process and to apply Data Matrix symbols to their parts and products.
Molding techniques utilizing wax molds are shown and described, by way of example, in U.S. Pat. No. 4,556,528 issued to H. M. Gersch et al on Dec. 3, 1985 for xe2x80x9cMold And Method For Casting Of Fragile And Complex Shapesxe2x80x9d and U.S. Pat. No. 5,124,105 issued to J. Broughton et al on Jun. 23, 1992 for xe2x80x9cMethod Of Manufacturing A Wax Pattern Of A Bladed Rotorxe2x80x9d.
Numerous methods for cutting or embossing a representation of a Data Matrix symbol into a wax mold, however, have been tried without success. Stamp impression methods were found to deform wax molds in undesirable ways. That is to say, material displaced from an impression may likely be pressed into an adjacent impression or be raised upward to alter the surface contour of the part. Hot stamp methods have been known to fail because a practical device could not be developed that could provide the complex symbol structure or resolution required to the parts. Mechanical cutting devices have also been known to fail because the wax cuttings tend to stick to the cut surface and do not readily fall clear as they would when cutting a hard surface.
It is therefore an object of this invention to provide new and novel methods, apparatus and encoding symbology for direct part marking.
It is another object of this invention to provide new and novel apparatus and methods for casting encoded symbology directly into parts.
It is still another object of this invention to provide new and novel encoding symbology for casting directly into parts.
It is still another object of this invention to provide new and novel encoding symbology for forging directly into parts It is yet still another object of this invention to provide new and novel 2D encoding symbology for casting directly into parts.
It is yet still another object of this invention to provide new and novel 2D encoding symbology for forging directly into parts.
It is a further object of this invention to provide new and novel methods to automate existing manual part identification methods used in conjunction with mold and cast marking processes using ThermoJet(trademark) type solid modeling technology.
It is still a further object of this invention to provide a new and novel software interface between Data Matrix type symbol generation software and ThermoJet(trademark) type solid object printers to provides operators of same with the ability to add two-dimensional information (height or depth dimensions) to encoding symbology.
It is yet still a further object of this invention is provide new and novel formatting of Data Matrix(trademark) type encoding symbols so that illumination generated shadows can be made to appear in marking recesses to provide contrast needed for optimal decoding of the symbols.
It is yet still a further object of this invention is to provide new and novel formatting of Data Matrix(trademark) type encoding symbols so that illumination is reflected to or away from the reader lens by providing a difference in texture between the data cells and the substrate, said difference providing necessary contrast for optimal decoding of the symbols.
It is yet still a further object of this invention to provide means for the equipment operator to enter symbol carrier (insert or plug) selection information that includes both shape and size information for the encoding symbols.
It is yet still another object of this invention to provide new and novel means to convert encoding symbol generation information to a format that is recognized by CAD software used to drive ThermoJet(trademark) type solid object printers.
It is yet still another object of this invention to provide new and novel means to simultaneously generate a reverse image insert that can be used to protect wax mold inserts while being inserted into parent product molds.